Method for selectively depositing a layer on a three dimensional structure

ABSTRACT

A method may include providing a substrate having a surface that defines a substrate plane and a substrate feature that extends from the substrate plane; directing an ion beam comprising angled ions to the substrate at a non-zero angle with respect to a perpendicular to the substrate plane, wherein a first portion of the substrate feature is exposed to the ion beam and wherein a second portion of the substrate feature is not exposed to the ion beam; directing molecules of a molecular species to the substrate wherein the molecules of the molecular species cover the substrate feature; and providing a second species to react with the molecular species, wherein selective growth of a layer comprising the molecular species and the second species takes place such that a first thickness of the layer grown on the first portion is different from a second thickness grown on the second portion.

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/336,893, filed Jul. 21, 2014, and further claimspriority to U.S. Provisional Patent Application No. 62/021,491, filedJul. 7, 2014, and to U.S. patent application Ser. No. 14/324,907, filedJul. 7, 2014, the entireties of which applications are incorporatedherein by reference.

FIELD

The present embodiments relate to substrate processing, and moreparticularly, to processing apparatus and methods for depositing layersby atomic beam or molecular beam deposition.

BACKGROUND

Many devices including electronic transistors may have three dimensionalshapes that are difficult to process using conventional techniques. Thetopology of such devices may be up-side down, re-entrant, over-hanging,or vertical with respect to a substrate plane of a substrate in whichsuch devices are formed. In order to process such devices such as togrow layers on such topology, improved techniques may be useful thatovercome limitations of conventional processing. For example, doping ofsubstrates is often performed by ion implantation in which substratesurfaces that may be effectively exposed to dopant ions are limited byline-of-site trajectories of the ions. Accordingly, vertical surfaces,re-entrant surfaces, or over-hanging surfaces may be inaccessible tosuch dopant ions. It is with respect to these and other considerationsthat the present improvements have been needed.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended asan aid in determining the scope of the claimed subject matter.

In one embodiment a method may include providing a substrate having asurface that defines a substrate plane and a substrate feature thatextends from the substrate plane. The method may also include directingan ion beam comprising angled ions to the substrate at a non-zero anglewith respect to a perpendicular to the substrate plane, wherein a firstportion of the substrate feature is exposed to the ion beam and whereina second portion of the substrate feature is not exposed to the ionbeam. The method may also include directing molecules of a molecularspecies to the substrate wherein the molecules of the molecular speciescover the substrate feature, and providing a second species to reactwith the molecular species, wherein selective growth of a layercomprising the molecular species and the second species takes place suchthat a first thickness of the layer grown on the first portion isdifferent from a second thickness grown on the second portion.

In a further embodiment, a method of selectively doping a threedimensional substrate feature on a substrate may include directing anion beam comprising angled oxygen ions to the substrate at a non-zeroangle with respect to a perpendicular to a substrate plane, wherein afirst portion of the substrate feature is exposed to the ion beam andwherein a second portion of the substrate feature is not exposed to theion beam. The method may also include directing molecules of a molecularspecies that includes a dopant species to the substrate wherein themolecules of the molecular species cover the substrate feature, whereinthe directing the ion beam and directing the molecules generatesselective growth of a dopant oxide layer comprising the dopant on thefirst portion but not on the second portion.

In an additional embodiment, a method of selectively doping a threedimensional substrate feature on a substrate may include exposing thesubstrate to an oxide plasma wherein the substrate feature is coveredwith a sub-monolayer of oxygen. The method may also include directing anion beam comprising angled ions to the substrate at a non-zero anglewith respect to a perpendicular to a substrate plane, wherein a firstportion of the substrate feature is exposed to the ion beam and whereina second portion of the substrate feature is not exposed to the ionbeam, wherein the sub-monolayer of oxygen is removed in the firstportion and the sub-monolayer of oxygen remains in the second portion.The method may also include directing molecules of a molecular speciesthat includes a dopant to the substrate wherein the molecules of themolecular species cover the substrate feature, wherein the directing theion beam and directing the molecules generates selective growth of adopant oxide layer comprising the dopant on the second portion but noton the first portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts a processing apparatus according to embodiments of thepresent disclosure;

FIG. 1B and depicts details of another processing apparatus according toadditional embodiments of the disclosure;

FIGS. 2A to 2D depict a sequence of operations for selective growth of alayer using a processing apparatus according to embodiments of thedisclosure;

FIG. 2E illustrates a close-up of a portion of a before processingaccording to the operations of FIGS. 2A to 2D;

FIG. 2F depicts the state of the substrate of FIG. 2E after processingthrough the sequence of operations of FIGS. 2A to 2D;

FIGS. 3A to 3C illustrate exemplary operations involved in selectivedeposition of a layer in which angled ions are used to suppressdeposition in impacted portions of substrate structures;

FIG. 3D depicts an alternative implementation of the operation of FIG.3B;

FIGS. 4A to 4C illustrate exemplary operations involved in selectivedeposition of a layer in which angled ions are used to enhancedeposition in impacted portions of substrate structures;

FIG. 5A is a top plan view of a substrate and extraction plate that isused to provide an ion beam to a substrate for a selective depositionprocess;

FIG. 5B is a top plan view of the substrate of FIG. 5A after provisionof a molecular beam subsequent to the ion beam;

FIG. 5C depicts a side view of the substrate at the same instance asthat shown in FIG. 5; and

FIG. 6A and FIG. 6B depict a side view and end view, respectively of asubstrate after treatment by multiple exposures to angled ions accordingto additional embodiments.

DETAILED DESCRIPTION

The present embodiments are related to techniques for processing asubstrate including forming thin layers on substrate features of asubstrate. The substrate features of the substrate may extend from asubstrate plane, and may form such structures as three dimensionallines, fins, pads, pillars, walls, trenches, holes, domes, bridges,cantilevers, other suspended structures, and the like. The embodimentsare not limited in this context. Moreover, these features may becollectively or individually referred to herein as a “three dimensional”feature or features. A thin layer that is formed on a substrate featuremay be a layer provided for doping, insulation, for encapsulation, orfor other purposes.

In various embodiments, a thin layer may be formed by a modified atomiclayer deposition or by modified molecular layer deposition process,which techniques may share characteristics common to conventional atomiclayer deposition (ALD) or conventional molecular layer deposition (MLD)except where otherwise noted. The present embodiments provide novelimprovements over conventional ALD and MLD that facilitate formation onthree dimensional substrate features in which surface topography may besevere, such as that described above.

In some embodiments, such as formation of a doping layer using ALD orMLD, a series of operations may be performed in which multiple layersare formed on substrates that may include three dimensional features. Inaddition, the formation of each layer may involve multiple operationssuch as those characteristic of an ALD or MLD process. In oneimplementation for doping a substrate using a deposited layer formed byALD or MLD, a surface of the substrate feature may first be cleaned toremove native oxide, which may involve providing a plasma using suchspecies as hydrogen, oxygen, and/or ammonia radicals and molecularhydrides such nitrogen triflouride, arsine, and phosphine.

Secondly, a conformal plasma enhanced atomic layer deposition of dopantoxides may be performed to form a dopant oxide layer on a substratefeature. This ALD process may involve deposition of species that includearsenic, boron, phosphorus, arsenic oxide, phosphorus oxide, boronoxides and/or doped silicon oxides such as silicon arsenic oxide,silicon phosphorus oxide, and silicon boron oxides. In particular, theseoxides may be deposited using molecular precursors such as arsine,phosphine, and diborane together with plasma-generated atomic beams thatcontain hydrogen, oxygen, nitrogen, and/or ammonia.

In a subsequent operation, a sealing layer such as silicon nitride maybe deposited using a combination of a molecular beam containing silane,for example, and another beam containing nitrogen, hydrogen, and/orammonia. Once the native oxide is removed from a substrate feature to bedoped and the dual layer of dopant oxide and sealing nitride isdeposited dopants from the dopant oxide layer may be driven into thesubstrate feature using a known technique such as rapid thermalannealing.

In various embodiments of the disclosure, a layer or plurality of layersmay be selectively formed on a substrate feature in a manner that theselectively formed layer has a first thickness in a first portion of thesubstrate feature that is different than a second thickness of the layerin a second portion of the substrate feature. For example, in anapplication for doping just a target portion of a three dimensionalsubstrate feature, a selectively grown layer comprising a selectivelygrown dopant oxide material may be deposited to a target thickness on afirst, target portion of the three dimensional substrate feature, whileon a second portion of the substrate feature outside of the targetportion, the dopant oxide material may be thinner or non-existent. Inthis manner, when the selectively grown layer is annealed to drive indopants, just a region of the substrate feature that is adjacent thetarget portion may be doped, thus forming a selectively doped region.

In various embodiments of the disclosure, as detailed below, thisselective deposition is facilitated by the use of angled ions that canbe selectively directed to a first portion or target portion of asubstrate feature without impinging on portion(s) of the substratefeature outside of the target portion. The directing of angled ions maybe used in conjunction with other operations to create novel ALD or MLDprocesses that selectively grow a layer or plurality of layers on athree dimensional substrate feature without the use of a mask. As usedherein, unless otherwise noted or qualified by the context, the term“layer” may refer to a sub-monolayer, a monolayer of a material, or mayrefer to a thin coating or film that has the thickness of manymonolayers. Thus, in some instances, a selectively grown “layer” may becomposed of a single monolayer that is formed over target portions of asubstrate or may be composed of multiple monolayers. Moreover,consistent with various embodiments of the disclosure, a layer that hasthe thickness of many monolayers may be formed in amonolayer-by-monolayer-by-monolayer fashion as in conventional ALD orMLD processes. However, the present embodiments also cover selectivegrowth of layers having the thickness of multiple monolayers in which alayer is not grown in a monolayer-by-monolayer fashion.

FIG. 1A depicts a processing apparatus 100 arranged according to variousembodiments of the disclosure. The processing apparatus 100 may beemployed to selectively grow a layer on a three dimensional structure.The processing apparatus 100 includes a source assembly 102 and aprocess chamber 104 adjacent the source assembly. The source assembly102 may include a plasma chamber (not separately shown) that generates aplasma from which angled ions 106 may be extracted and provided to asubstrate 108 disposed in the process chamber 104. The source assembly102 may further include a molecular source (not shown) that may providea molecular beam of a molecular species 110, which may be unionized, tothe substrate 108. It is to be noted that the molecular beam 110 may becomposed of molecules that stream toward the substrate 108 in a mannercharacteristic of a neutral gas, and therefore may not exhibitdirectionality that is characteristic of the angled ions 106. In someembodiments, the source assembly 102 may include additional plasmasources which may provide additional ions (not shown) to the substrate108 in an angled or non-angled manner. The source assembly 102 mayfurther include an additional molecular source(s) (not shown) to provideadditional molecular species to the substrate 108. As detailed below, insome embodiments, the angled ions 106 and molecular species 110 may beprovided in a manner that selectively promotes atomic layer-by-atomiclayer growth of an overall layer in certain portions of a substrate,where the regions in which layer-by-layer growth takes place mayexperience growth similar to that provided by conventional ALD or MLDtechniques. In other embodiments, the angled ions 106 and molecularspecies 110 may be provided in a manner that inhibits such atomiclayer-by-atomic layer growth in regions impacted by the angled ions 106.Thus, unlike conventional ALD or MLD techniques that may produceblanket, non-selective growth, the processing apparatus 100 facilitatesselective deposition of layers that may be formed in amonolayer-by-monolayer fashion. This is accomplished by the treatment ofa substrate with a combination of angled ions and molecules of amolecular species. As detailed below, in different implementations theangled ions may be inert ions or reactive ions.

As further illustrated in FIG. 1A an assembly 112 is disposed betweenthe source assembly 102 and process chamber 104. The assembly 112 may becomposed of at least one plate or structure that provides gascommunication between sources in the source assembly 102 and processchamber 104. For example, the assembly 112 may be composed of anextraction plate that is used to extract angled ions 106 from a plasmachamber and a showerhead or similar structure used to stream molecularspecies 110 to the substrate 108.

FIG. 1B depicts another processing apparatus 150 according to additionalembodiments of the disclosure. The processing apparatus 150 includes aplasma chamber 152 to form a plasma 153, a molecular source 154 tosupply molecular species, and a process chamber 156 to house a substrateholder 158, which is configured to support or hold a substrate 160. Theprocessing apparatus 150 also includes a plasma source 162, which mayinclude a plasma chamber power supply and applicator 163 or electrode togenerate a plasma according to known techniques. For example, the plasmasource 162 may, in various embodiments, be an in situ source or remotesource, an inductively coupled plasma source, capacitively coupledplasma source, helicon source, microwave source, arc source, or anyother type of plasma source. The embodiments are not limited in thiscontext. When gas is supplied by gas source 164 to the plasma chamber152 the plasma source 162 may ignite the plasma 153 as illustrated. Theplasma 153 may supply angled ions of a first species in the form of anion beam 168 to aid is selective deposition of a layer on a substratefeature.

The term “angled” ions as used herein refers to an assemblage of ionssuch as ions in an ion beam, at least some of which are characterized bytrajectories that have a non-zero angle of incidence with respect to aperpendicular to a plane P of substrate 160, as illustrated in FIG. 1B.For example, with reference to the Cartesian coordinate system shown,angled ions may have trajectories that form a non-zero angle withrespect to the Z-axis.

In some embodiments, the substrate holder 158 may be movable withrespect to at the plasma chamber 152 at least along a direction 170 thatis parallel to the Y-axis. In this manner, the substrate 160 may bemoved from a position adjacent the plasma chamber 152 to a positionadjacent the molecular source 154. Because of this movement, thesubstrate 160 may be alternately exposed to the ion beam 168 andmolecular beam 174 which may form when molecules stream out of themolecular source 154. As detailed below, this may result inmonolayer-by-monolayer selective growth of a material in target portionsof a three dimensional substrate feature. As shown in FIG. 1B, it is tobe noted that physical isolation may be provided between differentportions of the process chamber 156 so that species from the plasmachamber 152 are kept from the substrate 160 when the substrate 160 isadjacent the molecular source 154 and species from species frommolecular source 154 are kept from the substrate 160 when the substrate160 is adjacent the plasma chamber 152. This is shown as the isolationwall 155.

In various embodiments, processing apparatus such as the processingapparatus 100 and processing apparatus 150 may be operated at pressureranges that are lower than many conventional MLD or ALD systems.Exemplary pressure ranges include 1 to 100 mTorr, at which pressurerange a beam of ions may be directed to a substrate without sustainingmultiple collisions among ions before impacting a substrate. Thisfacilitates the ability to direct angled ions along fixed trajectoriesto target portions of a substrate feature that allow selectivedeposition of a layer as detailed below. Although FIG. 1B illustrates aprocessing apparatus 150 in which a plasma chamber and molecular sourceare separate, in various additional embodiments a source of angled ionssuch as a plasma chamber and a source of a molecular beam may becollocated such that angled ion species and molecular species may beprovided to the substrate to generate selective growth on substratefeatures without movement of the substrate.

FIGS. 2A to 2D depict a sequence of operations for selective growth of alayer using a processing apparatus 200 according to embodiments of thedisclosure. In this example, for the purposes of illustration, theprocessing apparatus 200 is shown in FIG. 2A to include a plasma chamber202 that may provide angled ions to a substrate 204 in the form of anion beam 206. The processing apparatus 200 is also shown in FIG. 2B toinclude a molecular source 208 that may provide a molecular beam 210. Asnoted previously such a molecular beam may be composed of molecules thatstream toward the substrate 204 in an undirected fashion. FIG. 2Eillustrates a close-up of a portion of the substrate 204 that showssubstrate features 212 before processing. The illustration in FIG. 2Fdepicts the state of the substrate 204 including substrate features 212after processing through the sequence of operations of FIGS. 2A to 2D.In particular examples, the substrate features 212 may constitute finstructures from which fin-type field effect transistors (finFETs) are tobe formed. As shown in FIG. 2A and FIG. 2B, for example, the substrate204 may be sequentially subjected to the ion beam 206 that directsangled ions to the substrate 204, and also to molecular beam 210. Thissequence of operations may constitute a process cycle that is used toform a layer of a material, such as a monolayer of a dopant oxide. Thissequence of operations as illustrated in FIGS. 2A and 2B may be repeatedin at least one additional process cycle such as shown in FIGS. 2C and2D to form an additional layer of material or monolayer of material. Inparticular, angled ions of the ion beam 206 may selectively impinge oncertain portions of the substrate features 212 and may be prevented fromimpinging on other portions of the substrate features 212, as discussedin more detail below with respect to FIGS. 3A to 4C. In conjunction withthe molecules provided by the molecular beam 210, a result of thisselective processing may be formation of selective layers 214, whichform just on upper portions of the substrate features 212. An advantageof this approach is that this selective formation of selective layers214 may facilitate selective doping of the upper portions of substratefeatures 212 without the use of masks.

In additional embodiments, instead of a molecular source, a remoteplasma source may be used to provide radical species that are providedto a substrate 204 in an alternating fashion with a directed ion beamthat provides angled ions, in order to generate selective formation oflayers in desired portions of substrate features.

In accordance with different embodiments of the disclosure, angled ionsmay be used to selectively increase layer deposition or selectivelysuppress layer deposition in regions which are impacted by the angledions. FIGS. 3A to 3C illustrate exemplary operations involved inselective deposition of a layer in which angled ions are used tosuppress deposition in exposed portions of substrate structures. Forpurposes of illustration it may be assumed that the layer to be grown issilicon oxide. However, in other examples, the layer to be grown may bea dopant oxide that includes dopants such as boron, phosphorous orarsenic. In FIG. 3A there is shown an instance in which a substrate 300is exposed to reactive ions 303 that may be extracted from a plasma 302.The substrate 300 includes substrate features 304, which extend from aplane P of the substrate as shown. The reactive ions may be oxygen,which form a sub-monolayer 306 on surfaces of the substrate features304. In the context of forming a compound material by ALD or MLD wherethe compound material comprises two or more different elements such assilicon oxide, a sub-monolayer may denote a layer of a first elementthat may react with a layer of a second element to form a monolayer ofthe compound. For example, during deposition of a binary compound suchas silicon oxide the layer to be formed is deposited by the repetitionof two different half-cycles. After each half-cycle, a fixed amount ofreactive species supplied by a first precursor remains on the substratesurface. Ideally, though not necessarily, a single monolayer of a firstspecies may be produced after a first half cycle. In the presentcontext, this single monolayer of a first species of a compound to beformed is referred to as a “sub-monolayer” because the full monolayer ofthe compound requires the addition of second species to react with thefirst species. Thus, atoms of the sub-monolayer of first species may bereacted with atoms or molecules of the second species supplied in thenext half cycle. In each half-cycle, subsequent to supplying a givenspecies, a purge can be performed to remove any unreacted species of thedepositing material. The total amount of material reacted in a cycle maythus be equivalent to a sub-monolayer of each of the first species orsecond species.

In a particular example, in embodiments in which the substrate 300 is asemiconductor substrate such as silicon or silicon:germanium, thesub-monolayer 306 may be composed of oxygen that is bonded to surfacesilicon atoms of the substrate 300 and may subsequently react with asub-monolayer of silicon-containing molecules to form a monolayer ofsilicon oxide.

In FIG. 3B there is shown a subsequent operation in which angled ions312 are directed to the substrate 300 when the substrate features 304are covered with the sub-monolayer 306. Referring again to FIG. 1B, theangled ions 312 may be generated when ions such as hydrogen ion areextracted from a plasma such as through an extraction aperture 176 of anextraction plate 178. Known extraction plates may modify a plasma sheathboundary in the region adjacent an extraction aperture. This may cause acurvature in the plasma sheath boundary that causes at least some ionsto exit the plasma over angle(s) that are not perpendicular to asubstrate plane, for example. This is shown for the plasma 308, whichfor simplicity is depicted without structural features of a plasmachamber, such as the aforementioned extraction plate 178. Asillustrated, a curved plasma sheath boundary region 310 may form next toan extraction aperture (not shown), leading to the generation of theangled ions 312. It is to be noted that the angled ions 312, althoughdepicted in a pair of trajectories, may be characterized by an ionangular distribution. The term “ion angular distribution” refers to themean angle of incidence of ions in an ion beam with respect to areference direction such a perpendicular to a substrate, as well as tothe width of distribution or range of angles of incidence centeredaround the mean angle, termed “angular spread” for short. In someexamples, the ion angular distribution may be a single mode in which thepeak in number of ions as a function of incidence angle is centeredaround a perpendicular to the plane P. In other examples, the ionangular distribution may involve a mean angle that forms a non-zeroangle with respect to a perpendicular to the plane P of the substrate300. In particular examples, the ion angular distribution of angled ions312 may be a bimodal distribution of angles of incidence. For example,the angled ions 312 in the example of FIG. 3B may have trajectorieswhere the greatest number of trajectories are centered at two angularmodes. In various embodiments, by controlling apparatus settings such asplasma power, plasma chamber pressure, and so forth, the separationbetween peaks of a bimodal distribution may be varied. For example, thepeak angles may set at angles between +/−15 degrees with respect toperpendicular to the plane P, +/−30 degrees with respect toperpendicular, +/−45 degrees with respect to perpendicular, or +/−75degrees with respect to perpendicular, to illustrate a few examples.However, the embodiments are not limited in this context.

As a result, the angled ions 312 may impact a first portion of thesubstrate features, which may be termed an exposed portion 314 of thesubstrate features 304, and which includes upper regions of sidewalls316 as well as top surfaces 318. In some examples, the angled ions 312may be hydrogen ions that are effective to react with oxygen to removethe oxygen in the exposed regions according to the reaction 2H+0>H₂O. Insome examples the angled ions may be inert gas ions. The angled ions 312may be provided at an ion energy and ion dose that is effective toremove the oxygen species that constitute the sub-monolayer 306 in theexposed portion 314 as shown. However, due to the three dimensionalnature of the substrate features 304, the angled ions 312 may beshadowed from impacting certain regions of the substrate features, whichare shown as a second portion of the substrate features 304 that may betermed an unexposed portion 320. For example, a first substrate featuremay be shadowed by adjacent substrate features such that upper portionsof the adjacent substrate features block angled ions 312 from impactinglower portions of the first substrate feature. For example, dependingupon the angle(s) of incidence of angled ions 312, the spacing S betweenadjacent substrate features, and the height H of substrate features 304,the extent of the unexposed portion 320 may vary. The unexposed portion320—may include lower regions of the sidewalls 316 as well as lowersurfaces 322, as shown. Accordingly, the sub-monolayer 306 may remainintact in the unexposed portion 320.

In some implementations a beam blocker (not shown) may be positionedinside a plasma chamber adjacent an extraction aperture, which may havethe effect of creating a pair of angled ion beams that may constitute abimodal distribution of ions. FIG. 3D depicts an alternativeimplementation of the operation of FIG. 3B. In this implementation anextraction apparatus 350 is employed to extract ions from the plasma 308and direct the ions to the substrate 300. As illustrated the extractionapparatus 350 includes an extraction plate 354 that defines anextraction aperture 348. A beam blocker 352 is disposed adjacent theextraction aperture and within a plasma chamber (not shown). The beamblocker 352 and extraction plate 354 together modify the shape of aplasma sheath boundary 356 such that two menisci are formed, shown asthe meniscus 358 and meniscus 360. Ions that exit the plasma 308 fromthe meniscus 358 form the ion beam 362, while ions that exit the plasma308 from the meniscus 360 form the ion beam 364. These two ion beams maystrike the exposed portions 314 of the substrate features 304 andprevent formation of a sub-monolayer in the manner as described abovewith respect to angled ions 312.

For a fixed set of substrate features in which the relative size, shapeand spacing of substrate features does not vary, in order to vary theextent of the unexposed portion 320 in which the sub-monolayer 306remains intact, the gas pressure in a plasma chamber, plasma power,width of extraction aperture, among other features may be varied. Thesevariations may vary the shape of plasma sheath boundary region which inturn may alter the ion angular distribution of the angled ions.

In a subsequent operation shown in FIG. 3C a molecular beam 324 may beprovided to the substrate 300. The molecular beam 324 may be provided ina manner that species of the molecular beam 324 impact all surfaces ofthe substrate features 304. In the example of selective formation ofsilicon oxide, the molecular beam 324 may be composed of silane (SiH₄)molecules or other silicon-containing molecules that are configured toreact with the oxygen species of sub-monolayer 306. The reaction ofsilane with oxygen in the sub-monolayer 306 may result in the formationof a monolayer of silicon oxide that adheres to the substrate 300. Theoperations shown in FIGS. 3A, 3B and 3C may be repeated to formadditional monolayers. In this manner, a selective layer 326 composed ofsilicon oxide may be formed in the unexposed portion 320 of thesubstrate features. However, in the exposed portion 314, which isdepleted of oxygen, a silicon oxide layer may fail to form since therequired oxygen is not present, or the amount of silicon oxide formedmay be reduced in proportion to the reduction of oxygen in the exposedportion 314.

In other embodiments, the sequence of operations shown in FIGS. 3A-3Bmay generally be followed except that instead of an oxygen plasma, anitrogen plasma may be provided to form a sub-monolayer of nitrogen,which may then be selectively removed in portions that are exposed toangled ions. Subsequently a silicon nitride monolayer may be formed byexposure to silane molecular beam, for example. The same applies forselective formation of a dopant oxide material, in which a molecularbeam of dopant-containing molecules may be provided instead of silane toreact with a sub-monolayer of oxide that remains on a second portion orunexposed portion of a substrate feature.

FIGS. 4A to 4C illustrate exemplary operations involved in selectivedeposition of a layer in which angled ions are used to enhancedeposition in impacted portions of substrate structures. For purposes ofillustration it may be assumed that the layer to be grown is alsosilicon oxide. In the operation shown in FIG. 4A, it may be assumed thatan oxygen plasma 402 is generated in an apparatus that includes anextraction plate that generates a curved plasma sheath boundary region404. As illustrated, angled ions 406, which may be oxygen ions, areextracted and directed to the substrate 400. The substrate 400 ischaracterized by substrate features 408, which extend from the plane Pas shown. The angled ions 406 may impact the exposed portion 410 thatlies in upper surfaces and upper regions of the sidewalls of thesubstrate features 408. The unexposed portion 412 may be unimpacted bythe angled ions 406. Accordingly, as shown in FIG. 4B, a sub-monolayer414 of oxide may form in the exposed portion 410. In some circumstances,the unexposed portion 412 may still be exposed to some oxygen when theangled ions 406 are directed to the substrate 400. In this manner, someoxygen ions may form a depleted oxygen sub-monolayer 416, which containsfewer oxygen species per unit area as compared to sub-monolayer 414. Forexample, the depleted oxygen sub-monolayer 416 may contain 80% or 90%fewer oxygen species as compared to sub-monolayer 414.

Turning now to FIG. 4C there is shown a subsequent operation in which amolecular beam 420 is provided to the substrate 400. In this operation,the molecular beam 420, which may be silane, may react with any oxygenspecies present on the substrate features 408. Thus, a monolayer 422 ofsilicon oxide may form in exposed portion 410 while less than amonolayer deposit, shown as layer 424 may form on unexposed portion 412.By proper adjustment of experimental conditions, it may be possible tocompletely suppress oxygen formation in the unexposed portion 412, suchthat a silicon oxide layer is just selectively deposited on the exposedportion 410.

In various additional embodiments an extraction plate may be arranged toprovide additional selectivity for ALD growth in which monolayer growthmay be restricted to certain sides of a substrate feature as well ascertain regions or portions of a given side of a feature. In theseembodiments, a sidewall of a given substrate feature may constitute afirst portion that receives angled ions, while an endwall of thesubstrate feature may constitute a second portion that does not receiveangled ions. FIG. 5A is a top plan view of a substrate 500 andextraction plate 502 that is used to provide angled ions to thesubstrate as part of a selective deposition process formonolayer-by-monolayer growth. The extraction plate 502 includes anextraction aperture 504 that is elongated along the X-axis. Theextraction aperture 504 may, for example, extend over an entire width Wof the substrate 500 along the X-axis so that ions may be directed alongthe entire width W at a given instance. By scanning the substrate 500along the Y-axis with respect to the extraction aperture 504, ions maybe provided over the entire substrate.

In FIG. 5A, and ion beam 506 may be extracted through the extractionaperture 504 and directed toward the substrate 500 (into the page ofFIG. 5A). The ion beam 506 is illustrated by different arrows whosetrajectories illustrate exemplary trajectories of the ion beam asprojected in the X-Y plane. It is to be noted that the ions of ion beam506 may be angled with respect to the Z-axis as in FIG. 4A. As shown, amajority of the trajectories of ions of the ion beam 506 are alignedparallel to the Y-axis. A set of substrate features 508 are illustratedthat have a sidewall 510 and an endwall 512 that extends perpendicularlyto the sidewall 510.

Ions having the trajectories oriented parallel to the Y-axis may impingeupon sidewalls 510 of substrate features 508, which are orientedparallel to the X-axis. In contrast, the endwalls 512 of the substratefeatures 508, which are oriented parallel to the Y-axis, may receivelittle or no ion bombardment.

In the case where the ion beam 506 comprises angled ions that areeffective to enhance monolayer growth, as in FIG. 4A, growth maytherefore be selectively enhanced along sidewalls 510 over endwalls 512.Thus, a molecular beam that reacts with portions of the substratefeatures 508 that received ion bombardment from ion beam 506 may beprovided in an additional operation, as generally depicted in 4C. FIG.5B is a top plan view of the substrate 500 after provision of amolecular beam subsequent to the ion beam 506. As shown, a monolayer 514selectively is formed along the sidewalls 510, but not along theendwalls 512. This is further shown in FIG. 5C, which depicts a sideview (not a cross-section) of the substrate 500 at the same instance asthat shown in FIG. 5B.

In the example of FIGS. 5B and 5C angled ions are used to selectivelytreat sidewalls 510 over endwalls 512 and to selectively treat upperportions of sidewalls with respect to lower portions of the sidewalls.Thus, the example of FIGS. 5B and 5C indicates a compound type ofselectivity afforded by the present embodiments where just certainportions of certain sides of a substrate feature are treated. However,other embodiments provide other types of selectivity. For example, inone implementation whole sidewalls may be exposed to angled ions insteadof upper regions of sidewalls alone.

In other examples, whole endwalls may be exposed to angled ions whilejust upper regions of sidewalls are exposed to ions. FIG. 6A and FIG. 6Bdepict an example of this type of selective monolayer growth. FIG. 6Aand FIG. 6B depict a side view and end view, respectively of a substrate600 having substrate features 602 upon which a selective layer 608 isgrown. The selective layer 608 may be a monolayer of plurality ofmonolayers that are grown in process as generally depicted in FIGS. 4Ato 4C where selective growth is promoted by exposure to angled ions. Asshown the selective layer 608 completely covers the endwalls 606 andcovers upper portions of sidewalls 604. This may be accomplished bydirecting angled ions (not shown) through an extraction plate in a firstexposure in which the endwalls 606 are arranged parallel to thetrajectories of the angled ions, rotating the substrate 600 by 90degrees within the X-Y plane, and directing angled ions in a secondexposure in which the trajectories of angled ions are parallel to thesidewalls 604.

Moreover, instead of promoting monolayer-by-monolayer growth on certainsides of a substrate feature that are exposed to angled ions as shown inFIGS. 5B and 5C, angled ions may be used to suppress monolayer-bymonolayer growth on those sides of a substrate feature exposed to theangled ions.

In other embodiments, instead of providing a beam of oxygen ions, anglednitrogen ions may be directed to substrate features to selectively forma sub-monolayer of nitride that is effective to react with silane toform a selectively deposited silicon nitride layer. Moreover, in otherembodiments, instead of providing a molecular beam of silane, in theoperation shown in FIG. 4C a molecular beam containing a dopant may beprovided to react with an oxide sub-monolayer to form a selectivelydeposited layer of dopant oxide.

In the above manner, the present embodiments may be employed toselectively form layers in target portions of substrate features byemploying angled ions. As noted the present embodiments provideflexibility to either enhance or suppress layer formation in portionsthat are impacted by ions. This allows different regions of substratefeatures to be targeted for selective growth, such as upper regions orlower regions of substrate features.

Although the above examples illustrated formation of silicon oxide, thepresent embodiments extend to formation of doped oxides, nitrides, andother materials that may be formed in a layer-by-layer process. Inaddition, the present embodiments may be employed to selectively deposita layer stack of different materials on a substrate structure. Such alayer stack may include, for example, a doped oxide layer, and anencapsulating nitride layer, which may be employed in a process to forma doped region in underlying substrate features.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure may be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

What is claimed is:
 1. A method, comprising: providing a substratehaving a surface that defines a substrate plane and a substrate featurethat extends from the substrate plane, the substrate feature including asidewall, the sidewall extending perpendicularly to the substrate plane;directing, from a plasma, an ion beam comprising angled ions to thesubstrate at a non-zero angle with respect to a perpendicular to thesubstrate plane, wherein an upper portion of the sidewall is exposed tothe ion beam and wherein a lower portion of the sidewall is not exposedto the ion beam, wherein the lower portion of the sidewall is shadowedby a second substrate feature, and wherein the angled ions do not impactthe lower portion of the sidewall; directing molecules of a molecularspecies to the substrate wherein the molecules of the molecular speciescover the substrate feature; and providing a second species to reactwith the molecular species, wherein selective growth of a layercomprising the molecular species and the second species takes place suchthat a first thickness of the layer grown on the upper portion of thesidewall is different from a second thickness of the layer grown on thelower portion of the sidewall.
 2. The method of claim 1, wherein theangled ions comprise reactive ions that constitute the second speciesand are configured to react with the molecular species, and wherein thefirst thickness on the upper portion of the sidewall is greater than thesecond thickness on the lower portion of the sidewall.
 3. The method ofclaim 2, wherein the angled ions are oxygen ions and the molecules aresilane.
 4. The method of claim 1, wherein the directing the ion beam tothe substrate and the directing molecules of a molecular species to thesubstrate together comprise a process cycle that is effective toselectively deposit a monolayer of a compound comprising the molecularspecies and a second species.
 5. The method of claim 4, furthercomprising performing at least one additional process cycle, wherein thelayer comprises a plurality of monolayers on at least one of the upperportion of the sidewall or the lower portion of the sidewall.
 6. Themethod of claim 1 wherein the layer is a selectively grown dopant oxide,wherein the first thickness is greater than the second thickness, themethod further comprising annealing the substrate, wherein a selectivelydoped region is formed in the substrate feature that is adjacent to theupper portion of the sidewall.
 7. The method of claim 1 wherein thesecond thickness is zero.
 8. The method of claim 2, wherein the angledions are nitrogen ions and the molecules are silane.
 9. The method ofclaim 1, wherein the substrate feature further comprises an endwall thatextends perpendicularly to the sidewall, wherein the directing the ionbeam comprises providing an extraction aperture in an extraction platethat is elongated along a first direction that is parallel to sidewall,wherein the angled ions impinge upon the upper portion of the sidewalland do not impinge upon the endwall.
 10. A method of selectively dopinga three dimensional substrate feature on a substrate, the threedimensional substrate feature including a sidewall, the sidewallextending perpendicularly to the substrate plane, the method comprising:directing, from a plasma, an ion beam comprising angled oxygen ions tothe substrate at a non-zero angle with respect to a perpendicular to asubstrate plane, wherein an upper portion of the sidewall is exposed tothe ion beam and wherein a lower portion of the sidewall is not exposedto the ion beam, wherein the lower portion of the sidewall is shadowedby a second substrate feature wherein the angled ions do not impact thelower portion of the sidewall; and after the directing the ion beam,directing molecules of a molecular species that includes a dopant to thesubstrate wherein the molecules of the molecular species cover thesubstrate feature, wherein the directing the ion beam and directing themolecules generates selective growth of a dopant oxide layer comprisingthe dopant on the upper portion of the sidewall but not on the lowerportion of the sidewall.
 11. The method of claim 10, further comprisingannealing the substrate wherein a doped region is formed in the threedimensional substrate feature adjacent the first portion.
 12. The methodof claim 10 wherein the substrate feature is a fin structure of a finFETdevice.
 13. The method of claim 10, wherein the three dimensionalsubstrate feature comprises an endwall that extends perpendicularly tothe sidewall, wherein the directing the ion beam comprises providing anextraction aperture in an extraction plate that is elongated along afirst direction that is parallel to sidewall, wherein the angled ions donot impinge upon the endwall.
 14. The method of claim 13, wherein thedirecting the ion beam comprises directing the ion beam in a firstexposure, the method further comprising: after the first exposure,rotating the substrate by 90 degrees within the substrate plane, anddirecting angled ions in a second exposure at a non-zero angle withrespect to the perpendicular, wherein a trajectory of the angled ions isparallel to the sidewall, wherein the endwall is exposed to the angledions in the second exposure, and wherein the dopant oxide layer forms onthe endwall.